There are a wide variety of filter assemblies which include a valve body through which a fluid flows past a spring loaded valve. A filter bowl may be removably attached to the valve body and to position a filter so that the fluid flows through the filter as it passes into and out of the valve body. The valve may be spring loaded toward closed or open positions. In some instances, such as in an anti-siphon valve, the spring biases the valve toward its closed position, and the valve is operatively associated with the filter bowl so that the valve automatically closes when the bowl is removed from the valve body for replacing the filter, for instance. Therefore, the flow of fluid is stopped to prevent leakage during filter replacement.
A problem with filter assemblies of the character described above is that the spring which loads the valve is exposed in the fluid flow path through the valve body. This causes the spring to become eroded because of contamination by the fluid, and the spring can become damaged because of continuous vibration when so exposed. This problem is particularly magnified in aircraft or aerospace applications wherein such filter/valve assemblies are designed as precise instruments and the spring is very delicate.
This problem of spring damage is further magnified in aerospace applications wherein the spring may break loose after severe erosion and enter a fluid system where further damage can result in a life threatening condition
This invention is directed to solving the above problems of spring erosion or damage by completely isolating the valve spring when the valve assembly is in operative condition.